Some people have a square or wide lower face because the chewing muscles at the angle of the jaw are large. Botox placed in those muscles, the masseters, can make them smaller over time and give the lower face a softer, slimmer outline. At Shield Dental Care in Burke, VA, Dr. Ghorbani offers masseter Botox for jaw slimming as part of our Botox service.
This is the same muscle we treat for grinding and clenching, but for a different reason. If your main concern is jaw soreness, headaches or wear on your teeth, see Botox for teeth grinding and clenching instead. Because it is the same muscle, treating it for one reason often affects the other.
Why the masseter changes the shape of your face
The masseter is the thick muscle at the back of each cheek that you can feel bulge when you bite down. Like other muscles, it can grow bulkier with heavy use, and in some people it is large enough to widen the lower face. When Botox reduces how hard the muscle works, the muscle gradually shrinks from lack of use, and the jawline looks narrower.
Botox can only change the muscle part of that width. It cannot change the shape of the jaw bone itself, so if your jaw is wide because of its bone structure, Botox will do little. We check which it is at the consultation, by looking and by feeling the muscle while you clench.
An off-label use, and where the FDA stands
As of September 2026, no botulinum toxin product is FDA-approved for jaw slimming in the US, so any masseter treatment for this purpose is off-label. That is legal and common, and we explain it as part of consent. In August 2026 the FDA accepted for review an application from the maker of BOTOX® Cosmetic to add “marked to very marked masseter muscle prominence” to its approved uses. Accepting an application for review is not an approval, and no decision has been announced yet.
What to expect
- Consultation. We look at your face at rest and while you clench, check your bite and jaw joints, and talk about the shape you are hoping for.
- Treatment. A few injections into each masseter, kept away from the front edge of the muscle and the smile muscles nearby. It takes a few minutes. The doses are much larger than for facial lines: a 2025 review describes roughly 24 to 60 units of BOTOX per side.
- Afterwards. You can go straight back to your day, with written aftercare.
How long the change takes, and how long it lasts
This is slower than wrinkle treatment. The muscle weakens within a couple of weeks, but it has to shrink before your face looks different, so the slimming appears gradually over the following weeks rather than days. As the effect wears off, the muscle slowly regains its bulk, so keeping the result means repeat treatment, no more often than every three months.
Researchers have asked whether repeated masseter injections affect bone density in the jaw. Some earlier, smaller studies reported reduced bone density in the jaw joint area after repeated treatment, while a 2025 placebo-controlled trial funded by the manufacturer found no negative effect after up to two treatments over a year. The question is not fully settled, which is one reason we use the lowest dose that works and leave sensible gaps between treatments.
Side effects
Tenderness or a bruise at the injection sites is common. For a few weeks, chewing tough or chewy food can tire the jaw more quickly. Less often:
- Uneven bulging. Part of the muscle can bulge when you clench if the effect is uneven. It is temporary, though in one large review of side effects it sometimes took several months to settle.
- An uneven smile. If the product reaches a nearby smile muscle, the smile can look briefly lopsided.
- A hollow or sagging look. A sunken cheek, or, rarely, some sagging of the skin along the jaw as the muscle shrinks, has been reported, more often in older patients.
All botulinum toxin products carry an FDA boxed warning: rarely, the effect can spread away from the injection site, causing trouble swallowing, speaking or breathing, vision problems or general muscle weakness, hours to weeks after treatment. These are medical emergencies.
Who should wait
- Anyone pregnant or breastfeeding, allergic to a botulinum toxin product, or with an infection where the injections would go.
- Anyone with a nerve-and-muscle condition such as myasthenia gravis, Lambert-Eaton syndrome or ALS.
- Tell us if you take blood thinners, have recently taken aminoglycoside antibiotics, or have had any botulinum toxin treatment in the last four months, including for grinding or TMJ pain.
Frequently Asked Questions
Is jaw slimming the same treatment as Botox for grinding?+
The same muscle is treated, but the goal is different. Jaw slimming aims to change the shape of the lower face, while grinding treatment aims to ease soreness and protect the teeth. Treating one often affects the other, and we will ask about both.
Is Botox for jaw slimming FDA-approved?+
Not as of September 2026. It is off-label for every brand. The FDA is reviewing an application to approve BOTOX Cosmetic for prominent masseter muscles, but no decision has been announced.
When will I see my jaw look slimmer?+
Gradually, over several weeks. The muscle has to shrink before the change shows, so it is slower than Botox for lines.
Will I still be able to chew normally?+
Yes, though for the first weeks tough or chewy food can tire your jaw sooner. It wears off as the effect fades.